1. Field of the Invention
This invention relates to a distance measuring device for automatic focus detection, particularly in leaf shutter type cameras, capable of measuring the distance of a plurality of objects existing at different positions.
2. Description of the Prior Art
Conventionally, distance measuring devices for cameras which automatically measure the distance to an object to be photographed have only one area in the field of view of the finder at a certain location (hereinafter called a "rangefinder spot"). In this case, if the rangefinder spot is of a small size, since one object is aimed at in the spot, its distance can be accurately measured without the influence of miscellaneous subjects within the neighbourhood. In some cases, however, it happens that instead of catching the subject of principal photographic concern, the distance measuring device is rendered responsive to the environment thereof. For example, when snapping two persons at a time, since the background between the persons reaches the spot, the camera is focused at infinity. In another device having a rangefinder spot of a large size, on the other hand, no matter how careful the photographer may be in aligning the device, it often measures the distance of a subject of little concern, for example, the foreground. Neither device has allowed accurate and reliable distance measurement while permitting relaxed shootings and, therefore, has failed to produce sharply focused photographs.
With the foregoing in mind, the object of the present invention is to provide a camera having a target area with a plurality of points to be measured in distance contributing to focal adjustment of a photographic lens, wherein means is provided for varying the number of points which contribute to the aforesaid focal adjustment of the photographic lens as a function of the object distance, thereby giving the advantage of assuring proper focal adjustment by very simple manipulation, since the number of subjects of photographic principal concern to be shot at one time and the background or the like are discriminately taken into account by the varying means.
Other objects of the invention will become apparent from the following description of an embodiment thereof.